A method of determining salinity of multi-phase fluids in a conduit includes exciting a sensing device to cause emission of electromagnetic waves of one or more frequencies into the multi-phase fluid. The method includes receiving transmitted or reflected electromagnetic waves from the multi-phase fluid. Furthermore, the method includes determining an intermediate parameter from the received electromagnetic waves. The method also includes obtaining estimated values of a plurality of parameters from the intermediate parameter. The estimated values comprise at least one of an estimated value of conductance, an estimated value of susceptance, an estimated value of differential conductance, an estimated value of differential susceptance, an estimated value of a real part of complex permittivity, and an estimated value of an imaginary part of complex permittivity. Salinity of the fluid is determined based, at least in part, on the estimated values of the plurality of parameters.